Merge changes from topic \'fp16-math-update\'
am: 20807a72d7

* commit '20807a72d7013cc6075ab62a34d7b815ef4defa9':
  Enable half tests for copysign, ilogb, nextafter
  Implement copysign, ilogb and nextafter for half
  Update RS headers with copysign, ilogb and nextafter
  Add copysign, ilogb and nextafter for half